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Bug #1687 HTTP Upload with IE3
Submitted: 1999-07-09 10:51 UTC Modified: 2002-06-16 08:33 UTC
From: php at tainted dot org Assigned:
Status: Not a bug Package: Other
PHP Version: 3.0.9 OS: Linux 2.0.x/glibc2.0
Private report: No CVE-ID: None
 [1999-07-09 10:51 UTC] php at tainted dot org
HTTP Uploading is built into PHP3.
HTTP Uploading is not supported by IE3.

Having a form with an entry like:

<INPUT ENCTYPE="multipart/form-data" NAME="userfile" TYPE="file">

Should make a browser provide a string gadget and a "Browse..." button to locally select a file to upload.

PHP3 normally accepts the data stream and puts it into
a temporary file.  When the form is submitted, the form
handler will have a variable of "$userfile" which contains
the name of the file PHP3 accepted it as, most
webmasters check to make sure that the $userfile is not "" or "none" and then proceed to fopen($userfile,...) for their

IE3 does not support HTTP Upload, but decides to give
the browser user a string gadget nevertheless.  The user
may enter the name of a file on the server "/etc/fstab" (or worse), which is sent to PHP3 from IE3 and the HTTP-Upload
portion of the form is not triggered.

This leaves the $userfile variable with the name of the
file the user has entered, which many scripts would just
fopen() and use.

I believe the only work around for this is to document
it and ensure to check the filename that it starts with
the php3 temporary path; other methods could likely be


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 [1999-07-10 14:06 UTC] markonen at cvs dot php dot net
My suggestion on this: change the file upload
functionality on the next major release (4.0?)
to fill the $userfile variable with the uploaded
filename relative to the php temp directory.
With our file upload implementation identical
otherwise, this would mean that a proper file
upload would never lead to $userfile value
that contains a slash or a backslash. 

My opinion is that the security implications of
this problem seem to warrant breaking of backward
compatibility. My proposed change would:

a) force the script implementors to rework their
code, taking into consideration the security
implications of this problem

b) allow script implementors to check for a safe
$userfile to fopen() by just looking for slashes
or backslashes in it
 [1999-07-10 14:14 UTC] rasmus at cvs dot php dot net
I don't think the suggestion in the second note is very good.  $userfile should be determined by the server and never by the client.  The fact that IE3 can get around this because it sucks is simply a bug and we need to check for that in an intelligent manner.  Once detected we simply set $userfile to "" or false
 [1999-11-14 04:00 UTC] joey at cvs dot php dot net
Has this gone anywhere?
 [2000-08-06 09:20 UTC]
Remind myself to look into this one.
 [2002-06-16 08:33 UTC]
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